Star Wars has introduced many concepts over the years, some loved by fans and others widely maligned. One of the most celebrated concepts was the idea of the Force, an incredible field of energy that spans the universe, allowing some -- like the Jedi or the Sith -- to tap into its power and perform incredible feats.
However, the Force also spawned one of the most despised additions to the franchise: midi-chlorians. Since their introduction in The Phantom Menace, midi-chlorians have been one of the most reviled additions to the Star Wars universe, with much of the fanbase and creatives behind the franchise doing their best to ignore them.
Even Luke Skywalker has come out against the idea of midi-chlorians. In the 2019 book Star Wars: The Secrets of the Jedi, written from the perspective of an older Luke, the Jedi Master had some less than encouraging things to say about the very concept.
"During the time of the Galactic Republic, the Jedi used science to explain why some of us feel the Force more strongly than others," Luke stated. "Prospective younglings were tested by the Jedi Order for midi-chlorians -- microscopic life-forms that reside in all living cells and impart the will of the Force to their hosts. Those with a high number of midi-chlorians were able to hear the will of the Force more clearly than others. Personally, I've never been one to worry about how exactly the Force whispers to me. All that matters to me is that it still does."
It's understandable why many dislike the concept of midi-chlorians. No matter how it's portrayed, the concept makes the Force lose some of the mysticism that attracted people to it in the first place. It also reduces the potential accessibility to the Force; instead of being highly spiritual allowing such a connection to come to pass in anyone, being a Jedi or Sith all comes down to winning the genetic lottery.
On the other hand, though, the idea of there being some sort of scientific way of measuring the Force would be fairly sensible for a civilization studying them for thousands of years. The Jedi and Sith of old having some way of detecting and quantifying Force-sensitivity would hardly be implausible, given their extensive studies on the energy field they all make use of. In addition to this plausible explanation, quite a few fans have also misinterpreted what the original explanation of midi-chlorians meant, believing it to mean that the Force is a product of space bacteria.
The Mortis arc of Star Wars: The Clone Wars helped fix the confusion by stating that the Force itself is still a mystical energy field and that midi-chlorians are the connection between the Living Force in individuals and the Cosmic Force that spans the universe. And regarding the genetic lottery argument, a lot of people forget that the Force has always had an element of blood to it. In The Empire Strikes Back, Vader and the Emperor feared Luke because he was the son of Anakin Skywalker, which heavily implied that Luke's bloodline was an important part of his Force-sensitivity.
Of course, the original idea of midi-chlorians wasn't necessarily the most well thought out concept. However, the hatred for the concept can be overblown at times, and as Luke stated, they really don't mean that much to the grand scheme of the Force. No matter what, though, midi-chlorians will remain one of Star Wars' most controversial additions.